1. Field of the Invention
The present invention relates to a numerical control information generating apparatus for generating numerical control information from a before-machining shape and an after-machining shape of a workpiece.
2. Related Art Statement
A so-called numerically-controlled machine tool is arranged in a manner such that a machine tool is automatically controlled by numerical control information constituted by numerals and codes. The wide use of such machine tools has contributed greatly to automating machining operations, reducing machining cost and, shortening machining times.
The above-described numerically-controlled machine tool requires that information used to perform the numerical control operation be input prior to performing the machining operation. Recently, a numerical control information generating apparatus for generating numerical control information in accordance with data received in an interactive manner has been widely used in order to simplify the information input operation. In such a numerical control information generating apparatus, the numerical control information used to machine the subject workpiece is processed after inputting data denoting the material of the subject workpiece, the before-machining shape and the method of machining (the region to be machined, the cutting method, the cutting tool, the cutting conditions, the cutting order and the like). Furthermore, there has recently made available a numerical control information generating apparatus of a type in which numerical control information is generated after the method of machining has been automatically determined by inputting the before-machining shape and the after-machining shape of the workpiece.
FIGS. 1A and 1B are a block diagrams which illustrate a conventional numerical control information generating apparatus. Referring to these drawings, before-machining shape SA and after-machining shape SB input by an operator through a control panel 1 such as a keyboard are, via a data input section 2, respectively stored in a before-machining shape storing section 3 and an after-machining shape storing section 4. The before-machining shape SA stored in the before-machining shape storing section 3 and the after-machining shape SB stored in the after-machining shape storing section 4 are read by a feature extracting section 5. Thus, shape feature SC, which is a factor used to determine the machining method, is extracted so as to be stored in a feature temporarily storing section 6. On the other hand, machining method determining parameter SE which is also used to specify the machining method is been previously stored in a parameter storing section 19 so as to be read and stored by the parameter temporarily storing section 18.
The shape feature SC stored in the feature temporarily storing section 6 and the machining method determining parameter SE stored in the parameter temporarily storing section 18 are read by a feature discriminating section 7 so as to be subjected to a comparison. The result of this comparison is transmitted as feature comparison data SF to a machining method determining section 8 where the machining method SG is transmitted determined. The machining method SG thus-determined is read and then processed by a step data generating section 9 for processing data for each of the generating processes. The step data generating section 9 prepares step machining data SH for each of the generating processes including information denoting the cutting shape, the cutting tool, the cutting conditions and the cutting order for each of the processes. The step machining data SH for each of the generating processes processed by the step data generating section 9, the before-machining shape SA stored in the before-machining shape storing section 3 and the after-machining shape SB stored in the after-machining shape storing section 4 are read by a display control section 10 so as to be converted into display data SI. The display data SI is displayed on a display device 12 via a display data output section 11. The step machining data SH for each of the machining processes processed by the step data generating section 9 is read by a numerical control information generating section 13 so as to be encoded. As a result, a numerical control information SJ is processed so as to be output to a magnetic tape 15, a floppy disk 16 or a communication signal 17 via a numerical control information output section 14.
FIG. 2 is a flow chart which illustrates an example of the operation of an essential portion of the above-described conventional numerical control information generating apparatus.
First, the data input section 2 stores the before-machining shape SA and the after-machining shape SB, which have been input through the control panel 1, in the corresponding before-machining shape storing section 3 and the after-machining shape storing section 4 (Step S101). Then, the parameter temporarily storing section 18 reads and stores the machining method determining parameter SE from the parameter storing section 19 (Step S102). On the other hand, the feature extracting section 5 makes a comparison between the before-machining shape SA stored in the before-machining shape storing section 3 and the after-machining shape SB stored in the after-machining shape storing section 4. The feature extracting section 5 then extracts the shape feature SC, which serves as a factor for determining the machining method, from the shape data of the graphic elements which are necessary to perform the machining, so as to be stored in the feature temporarily storing section 6 (Step S103). When the feature discriminating section 7 has made a comparison between the shape feature SC stored in the feature temporarily storing section 6 and the machining method determining parameter SE stored in the parameter temporarily storing section 18 and subsequently the feature comparison data SF has been thereby processed, the machining method determining section 8 determines the machining method in accordance with the feature comparison data SF (Step S104). Thus, all of the processes are completed.
Reference is made to FIG. 3 for an example in which the more effective of either a face machining method or a longitudinal machining method is selected based on the before-machining shape and the after-machining shape input in the above-described apparatus of FIGS. 1A and 1B. The feature extracting section 5 extracts, as the shape feature SC serving as a factor for determining the machining method, an angle extending from the X-axis of the graphic element e an, X-directional length L of the graphic element e and size D of the cutting stock. The feature discriminating section 7 makes a comparison between the three factors A, L and D, which have been extracted by the feature extracting section 5 as the shape feature SC, and a limit value PA of the angle from the X-axis, a limit value PL of the X-directional length and a limit value PD of the size D of the cutting stock. Examples of the limit values PA, PL and PD are shown in FIG. 4. The machining method determining section 8 selects either the method of the face machining and the longitudinal machining method in accordance with the result of the above-made comparison. That is, if all the below conditions (1) to (3) are satisfied, the machining method of the graphic element e is determined to be face machining, and if at least one of them is not satisfied, the machining method of the graphic element e is determined to be longitudinal machining. EQU A.ltoreq.PA (1) EQU L&gt;PL (2) EQU D.ltoreq.PD (3)
However, the above-described conventional numerical control information generating apparatus encounters a problem in that the most suitable machining method cannot always be obtained because it is determined in accordance with a single parameter set as shown in FIG. 4. For example, a workpiece A having a long X-directional length and a short Z-directional length as shown in FIG. 5 can be broken or deformed if a heavy cutting load is more often applied to it in the Z-direction. Therefore, it is preferable that the face machining be performed in comparison to the usual machining. On the contrary, a workpiece B having a short X-directional length and a long Z-directional length as shown in FIG. 6 can be broken or deformed if a heavy cutting load is applied to it in the X-direction. Therefore, it is more often preferable that the longitudinal machining be performed by a larger quantity in comparison to the usual machining. However, since the one kind parameter set is provided for the conventional numerical control information generating apparatus as described above, the machining method for both the workpieces A and B is determined in accordance with the same parameters. Therefore, a problem arises in that an operator must establish the parameter whenever the machining method is determined or must modify the manufacturing process data or the numerical control information processed in accordance with the determined machining method to obtain the most suitable machining method for each of the workpieces.